Thin layer propagating slurry explosive

ABSTRACT

A cap-sensitive slurry explosive capable of propagating a high order detonation in thin layers and which has a high degree of safety for a cap-sensitive explosive. The slurry consists of an ultra-fine solid explosive suspended in an energetic, but nonself-explosive liquid matrix and contains no liquid explosive ingredient. The slurry resists dispersion in a variety of liquids including water and crude oil. In a preferred embodiment, the slurry includes penetaerythritol tetranitrate (PETN).

United States Patent Forrest Oct. 14, 1975 [54] THIN LAYER PROPAGATINGSLURRY 3,676,234 7/1972 Schwoyer 149/93 X EXPLOSIVE [75] Inventor:Charles D. Forrest, Hollister, Calif. Primary Examiner S tephenAttorney, Agent, or firm-David H. Semmes [73] Assignee: TeledyneMcComiick Sleph,

H II' t C l'f.

0 1S er a1 C [22] Filed: Jan. 31, 1974 Appl. No.: 434,754

References Cited UNITED STATES PATENTS 7/1969 Griffith et al. 149/93 Acap-sensitive slurry explosive capable of propagating a high orderdetonation in thin layers and which has a high degree of safety for acap-sensitive explosive. The slurry consists of an ultra-fine solidexplosive suspended in an energetic, but non-self-explosive liquidmatrix and contains no liquid explosive ingredient. The slurry resistsdispersion in a variety of liquids including water and crude oil. In apreferred embodiment, the slurry includes penetaerythritol tetranitrate(PETN).

1 Claim, No Drawings THIN LAYER PROPAGATING SLURRY EXPLOSIVE BACKGROUNDOF THE INVENTION As is known, certain explosives such aspenetaerythritol tetranitrate (PETN) for example, are hazardous whensubjected to modest physical abuse from impact or friction forces. Suchcompounds additionally do not have desired inertness toward crude oiland brine and dilute forms of many other well environmental material.Such materials additionally are hazardous in being highly inflammableand in many formulations are toxic.

BRIEF DESCRIPTION OF THE INVENTION The slurry of the present inventionis a new type of cap-sensitive slurry explosive capable of propagating ahigh order detonation in thin layers. The invention provides a safeexplosive in slurry form which may be used in oil well and gas wellformation fracturing, rock fracturing for in situ ore leaching,non-nuclear fracturing of oil shale formations, and explosive formationof fire lanes in terrain inaccessable to motorized equipment.

The slurry of the present invention is formulated to resist accidentalinitiation by adiabatic compression of gas bubbles which may beintroduced during loading and handling, and due to the good chemicalstability of the explosive formula, the slurry gives a high degree ofinertness toward crude oil and brine and dilute forms of most other wellenvironmental materials. The material of the presentinvention in firesis difficult to ignite, and once ignited, burns quietly with noexplosion. The ingredients comprising the slurry are non-toxic prior todetonation.

Additional advantages, objects and features of the invention will bemore readily apparent from the following detailed description of anembodiment thereof.

Example by weight) Sensitive Fine Particle PETN 50 6071 Ammonium NitrateSolution 0 80 Diethylene Glycol O Guar Gum or Poly-acrylamide 0.1 3.0Water Balance Cross-linking Agent As required The sensitive fineparticle PETN is disclosed in greater detail in my co-pendingapplication, Ser. No. 434,753, filed Jan. 31, 1974 entitled SENSITIVEFINE PARTICLE PETN.

The ammonium nitrate solution may, in certain instances, be replacedlargly by potassium, barium or sodium nitrate solution. The diethyleneglycol may be replaced largly by other soluble organic fuels such asformamide, diethyl formamide or other glycols and certain alcohols.Also, some portion of solid fuel may be included, i.e., fine coal,sulfur, gilsonite, or aluminum, ferro-phosphorous, ferro-silicon, etc.

A satisfactory cross-linking agent consists of Tyzor LA, which is atrademark preparation of E. I. DuPont de Nemours & Company, Inc. andwhich is known generally as Titanium-antimonium lactate, as illustratedin US. Pat. No. 3,622,408.

In the above example, the concentration of ammonium nitrate solution isnot critical. A 60% solution is convenient to use because the ammoniumnitrate stays completely in solution above 54F, which means thathandling is simplified over, for example, an solution which has asolidification temperature of about 136F, which would require expensiveheated storage. After blending withanti-freeze agent, such as diethyleneglycol, the solidification temperature is decreased.

This cap-sensitive explosive is capable of propagating a high orderdetonation in thin layers, i.e., one-thirty second inch when confinedbetween masonite, able to detonate completely in thin layerssimultaneously exposed to a hydrostatic pressure of 10,000 psi or aboveand a temperature of approximately 200F, does not cause headache duringhandling, and contains no liquid explosive ingredient. Further, slurryexplosive is unaffected when penetrated by British 303 ammunition from adistance of 75 to feet, even when backed by steel or aluminum. Slurryexplosive will slowly decom pose in a bonfire when unconfined, but byitself will not support combustion.

The purpose of this invention is to provide a safe explosive in slurryform which may be used in l the explosive fracturing of oil and gasreservoirs in order to increase formation permeability and thus increaserate of flow to wellbore; (2) the explosive fracturing of oil shaleformations to permit thermal recovery of petroleum products therefrom inan economical manner; (3) various military applications; and (4)non-incendiary line charges for the rapid construction of fire lanes tofight forest fires, particularly in terrain inaccessable to mechanizedequipment.

Ordinarily, PETN (penethaerythritol tetranitrate) is considered ahazardout explosive which is known to explode when subjected to modestphysical abuse from impact or friction forces. For example, in a droptest apparatus in which a small (i.e., approximately onetwentieth gram)sample of sensitized small particle PETN is placed on a hard tool steelanvil and impacted by a free fall hammer, also made of hard tool steeland weighing 2.143 kg, detonations of the PETN occur when the dropheight is only 2 cm. In other words, the impact sensitivity of the pure,dry PETN is 4.3 kg-cm. When this same PETN is compounded into thisslurry explosive in the proportions of 40% PETN/50% of a 60% ANsolution/9.5% DEG/0.5% guar and cross linked (5 drops/100g slurry) witha 50% solution of Tyzor LA in deionized water, the resulting explosivemixture is unaffected by repeated hammer drops from a drop height of63/5cm. Thus, in slurry form, the PETN is not exploded by an impact of136.3 kg-cm, which is more than 30 times the energy at which the PETNalone explodes. The slurry formula given in the above example detonatescompletely at high velocity under a hydrostatic pressure of 10,000 psiin a layer one-sixteenth inch thick by 2- /2 inches wide confinedbetween two sheets of A inch thick masonite.

The consistency of the slurry can be varied to suit the needs of aparticular requirement. The slurry can be provided in viscosity rangesfrom a thin milkshake to bread dough consistency. Rather thick slurryhas the amazing property of passing readily through a small (l/32 inchdiameter) orifice under low pressure and then reconsolidating withitself. This high degree of thixatrophy allows it to readily adapt to avariety of applications. It has been found that the detonation rate ofthe slurry is 21,400 feet per second in a layer thickness of 0.032inches (one-thirty second) with mild confinement. Atpressures up to10,000 psi, the slurry explosive with a thickness of 0.063 inch(one-sixteenth) detonates completely.

Manifestly, minor changes can be effected in the above-describedexamples without departing from the spirit and the scope of theinvention as defined in and limited solely by the appended claims.

I claim:

' l. A thin layer propagating slurry explosive compris-

1. A THIN LAYER PROPAGATING SLURRY EXPLOSIVE COMPRISING A MIXTURECONSISTING OF, BY WEIGHT: A. 40% SENSITIVE FINE PARTICLEPENETAERYTHRITOL TETRANITRATE (PETN), B. 50% OF A 60% AMMONIUM NITRITESOLUTION, C. 9.5% DIETHYLENE GLYCOL, D. 0.5% GUAR, AND E. 5 DROPS/100GSLURRY OF A 50% SOLUTION OF TITANIUM ANTIMONIUM LACTATE IN DEIONIZEDWATER AS A CROSS-LINKING AGENT.